1. Field of the Invention
This invention relates to a clutchless variable capacity swash plate compressor, and more particularly to clutchless variable capacity swash plate compressor to which torque of an engine is constantly transmitted.
2. Description of the Prior Art
Conventional clutchless compressors include a clutchless variable capacity awash plate compressor. In this compressor, the inclination angle of a swash plate varies with suction pressure to change the stroke length of each piston, whereby delivery quantity or capacity of the compressor is increased or decreased.
However, when a clutchless variable capacity awash plate compressor in which the minimum delivery quantity or capacity thereof is not equal to zero is employed as a clutchless compressor, an evaporator supplied with compressed refrigerant gas from the compressor has its surface frosted by being cooled by evaporation of the refrigerant gas when the compressor is under a low thermal load condition. As a result, it often happens that the evaporator is frozen, and ventilation is hindered, which results in degradation of cooling capability of the compressor.
To eliminate this inconvenience, there was proposed a method in which when thermal load on the compressor decreases (equivalent to a state of a clutch-type compressor in which a clutch therefor is disengaged), refrigerant gas is circulated within the compressor to thereby reduce the amount of refrigerant gas discharged from the compressor to zero (Japanese Laid-Open Patent Publication (Kokai) No. 7-286581).
However, this clutchless compressor uses a sleeve for closing a low-pressure side thereof, which is axially slidably fitted on a drive shaft. This sleeve, however, forms assembly with a bearing supporting the drive shaft, which prevents the drive shaft from being sufficiently preloaded. As a result, a lug plate fixedly fitted on the drive shaft for transmitting torque of the drive shaft to a swash plate becomes axially unstable, which causes the lug plate to vibrate, generating loud untoward noises. Especially when the compressor is in a high-load condition, in which the delivery quantity is large, the noises become louder since a spring for retaining the sleeve is expanded to decrease the preload applied to the drive shaft.
If the spring for retaining the sleeve is set to have an increased urging force, a load applied to a thrust bearing under a minimum delivery condition of the compressor is increased, and larger torque is required of the drive shaft. As a result, the power consumption is increased in the minimum delivery condition equivalent to the clutch-disengaged state of the clutch-type compressor. Therefore, an increase the urging force of the retaining spring cannot be a solution to the above problem.
Further, the bearing supporting the drive shaft abuts a cylinder block of the compressor via the sleeve. This produces a radial gap between the sleeve and the cylinder block, causing louder noises.
Moreover, components of the clutchless compressor including the cylinder block are complicated in construction. This makes it difficult to share component parts with a clutch-type variable capacity swash plate compressor.